a) Field of the Invention
The present invention relates to a planographic printing plate and a method of manufacturing a support therefor, and particularly to a planographic printing plate in which a part of a surface (back surface) not subjected to roughening treatment for application of a photosensitive resin layer in a planographic printing plate is roughened electrochemically to obtain a rough surface having an arbitrary shape (for example, a design pattern), and a method of manufacturing a support therefor.
b) Description of the Related Art
A planographic printing plate is mainly composed of an aluminum or aluminum alloy support (hereinafter simply referred to as an "aluminum plate") and a photosensitive resin layer. Heretofore, a so-called graining treatment for roughening the entire surface of a support to be brought into close contact with a photosensitive resin layer is carried out in order to make the adhesion between the support and the photosensitive resin layer good and to provide water retentivity to a non-image portion.
As specific means for this graining treatment, there are mechanical graining methods such as a sandblasting method, a ball graining method, a brush graining method using a nylon brush and an abrasive agent/water slurry, a honing graining method of blowing an abrasive agent/water slurry onto a surface of a support at a high pressure, etc., and chemical graining methods for roughening a surface with an etching agent formed of an alkaline agent or an acidic agent or a mixture thereof. There are further known electrochemical graining methods described in Japanese Patent Unexamined Publication Nos. Sho-52-58602, Sho-52-152302, Sho-54-85802, Sho-55-158298, Sho-58-120531, Sho-60-147394, Sho-56-28898, Sho-60-190392, Hei-1-5589, Hei-1-280590, Hei-1-118489, Hei-1-141094, Hei-1-148592, Hei-1-178496, Hei-1-188395, Hei-1-154797, Hei-2-235794, Hei-3-260100 and Hei-3-253600, electrochemical graining methods using a sinusoidal waveform AC electric source as described in Japanese Patent Unexamined Publication No. Sho-48-28123 and the specification of British Patent No. 896563, electrochemical graining methods using special waveform as described in Japanese Patent Unexamined Publication No. Sho-52-58602, methods using a mechanical graining method and an electrochemical graining method in combination as described in Japanese patent Unexamined Publication Nos. Sho-54-123204 and Sho-54-63902, a method using a mechanical graining method and a chemical graining method using a saturated aqueous solution of aluminum salt of mineral acid in combination as described in Japanese Patent Unexamined Publication No. Sho-56-55261, and so on.
Among the aforementioned various roughening methods, electrochemical roughening methods are known as methods in which: the shape of the resulting rough surface is controlled easily; a fine rough surface is obtained; and production equipment is simplified.
Because a roughened aluminum surface is soft in itself so that the surface abrades easily, an oxide film is formed by anodic oxidation and then a photosensitive resin layer is provided thereon. The thus treated surface of the aluminum plate is hard and excellent in durability against abrasion, so that the surface exhibits good hydrophilic property, water retentivity and property of adhesion to the photosensitive resin layer.
On the other hand, surface treating methods for building materials, name plates, etc. formed of aluminum are known widely and generally. As specific means for these treating methods, there is, for example, a treating method for manufacturing a pattern in an aluminum surface by electrolytic treatment in a de-smut solution as described in Japanese Patent Postexamination Publication No. Sho-60-15717, a treating method for forming a longitudinally striped film by the action of bubbles produced by application of AC electrolysis in an electrolytic bath after (mechanical, chemical or electrochemical) roughening of an aluminum surface as described in Japanese Patent Postexamination Publication No. Sho-60-11118, a treating method of the steps of: applying a resin solution onto a surface of a plate such as a name plate formed of a metal (for example, aluminum) in the form of a pattern such as a character pattern; drying the resin solution to form a protection film on the surface; and forming a pattern such as a character pattern by removing the protection film after electrolytic polishing in an electrolytic bath, as described in Japanese Patent Postexamination Publication No. Sho-61-54120, a treating method of the steps of: applying anodic oxide coating after treatment (resin treatment, mechanical/chemical polishing, hair-line/sand blasting, etc.) of aluminum; carrying out printing by using printing ink excellent in non-electroconductivity after drying; drying and hardening the printing ink by an anealing means; and forming a pattern such as a character pattern by electrodeposition coating to these surfaces, as described in Japanese Patent Postexamination Publication No. Hei-2-3718, a treating method of the steps of: supplying a pattern-producing matter (such as an oil dye, etc.) obtained by mixing/dispersing a powdered magnetic substance onto a liquid surface of a water bath in advance; making magnetic force produced by an electromagnet act on the magnetic substance in the pattern-producing matter to thereby reveal a predetermined pattern in the pattern-producing matter on the liquid; and making the predetermined pattern deposit onto an aluminum material subjected to anodic oxidation (inclusive of coloring treatment) after pre-treatment (degreasing/cleaning, etching, de-smutting, etc.) to thereby produce a pattern on the aluminum material, as described in Japanese Patent Postexamination Publication No. Sho-59-50198, and so on.
Further, surface treating methods for metals other than aluminum are known widely and generally. As specific means for these treating methods, there is, for example, a treating method adapted to the case of copper and comprising the steps of: marking a copper plate with a pattern such as a character pattern by a marking material having property of adhesion to the copper plate after pre-treatment (electrolytic film forming treatment, electrochemical film forming treatment, chemical treatment, soaking treatment) of the copper plate; forming a resist film not having a property of adhesion to the marking material but having a property of adhesion to the copper plate, on the other, not-marked portion of the copper plate; applying plating to the marked portion of the copper plate after removing only the marking material; and removing the resist film to thereby form a pattern such as a character pattern, as described in Japanese Patent Postexamination Publication No. Sho-60-41154, a treating method adapted to the case of stainless steel and comprising the steps of: printing a not-patterned portion of a stainless steel article with acid-resisting ink by screen printing; making a patterned portion corrode by etching to thereby form a cavity portion; and carrying out plating with the stainless steel article as an anode and gold, silver, copper, etc. as a cathode in the condition in which the bottom of the cavity portion is polished electrolytically and an acid-resisting solution is applied onto the portion other than the cavity portion to thereby form a plated layer of a metal such as gold, silver, copper, etc. on the bottom of the cavity portion, as described in Japanese Patent Unexamined Publication No. Sho-50-56334, treating methods adapted to the case of stainless steel and for forming a color pattern on a stainless-clad aluminum plate, as described in Japanese Patent Postexamination Publication Nos. Sho-53-39869 and Sho-56-10999, a treating method adapted to the case of stainless steel and for carrying out coloring treatment (coloring in a sulfuric acid-chromic acid solution, hardening of an oxide film) after applying mechanical patterning treatment (scribing, pressing with a jig having a pattern, drawing a pattern with a sharp knife, embossing treatment, etc.) to the back surface of a stainless steel plate, as described in Japanese Patent Unexamined Publication No. Hei-2-307629, and so on.
On the other hand, the entire surface having no photosensitive resin layer (back surface), of a planographic printing plate may be subjected to surface treatment. As specific means for this treating method, there is a method of treating the surface with an aqueous solution of alkali-metal silicate as described in Japanese Patent Unexamined Publication No. Hei-3-90388, a method of applying paint containing a surface toughening agent dispersed therein or carrying out mechanical treatment such as ball graining, honing graining, brush graining, etc. or carrying out powdering directly by using powder, as described in Japanese Patent Unexamined Publication No. Sho-62-1586, a method of carrying out heat fusion after applying resin particles substantially uniformly as described in Japanese Patent Unexamined Publication No. Hei-3-249652, a method of producing an embossed pattern on the whole by pressing an embossing roller from the back surface, as described in Japanese Postexamination Publication No. Sho-55-237, and so on.
Further, methods of realizing a design pattern in a portion of the back surface of a support for a planographic printing plate include an ink-jet method, a printing method, and so on.
In these methods, however, a portion of ink deposited by printing becomes swollen. Accordingly, these methods have not only a defect that the resulting printing plate is stuck to the photosensitive resin layer in the case of winding or stacking, but also a defect that ink is eluted at the time of development. In addition, these methods have a defect that equipmental cost required for preventing the elution of ink becomes enormous if the elution of ink is prevented by use of (UV- or thermo-)setting ink.
Further, there is a method of sticking a roller or plate having a realized design pattern to the back surface of a support for planographic printing plate. This method, however, has not only a defect that a design pattern portion of the roller or plate abrades but a defect that the plane flatness of the support is spoiled to make it difficult to attain the uniform characteristic of the coated layer in the case where a photosensitive resin layer is provided because a compressed portion of the support becomes swollen.